do i just post my work in the thread or do i have to specially sign up in a contest.

You don't have to formally sign up for the competition. You can start a thread in the "Work in Progress" section of the forum to post images of your work as it progresses if you want, but in order to be entered in the competition, you need to post your final image in the competition thread. Just look at the past competition threads and you will see how people are posting their entries.

You don't have to formally sign up for the competition. You can start a thread in the "Work in Progress" section of the forum to post images of your work as it progresses if you want, but in order to be entered in the competition, you need to post your final image in the competition thread. Just look at the past competition threads and you will see how people are posting their entries.